10 Hz to 30 Hz Oscillator w/Driver Circuit

Parts List:

ITEM Label on Schematic
PC Board
8-pin socket
Controller IC NE555 (8-pin) IC1
.47 uF Electrolytic Capacitor C1
.1uF or .01uF Ceramic Capacitor C2
500K Multiturn Potentiometer R1
(2) 100K Resistors R2 & R4
1K Resistor R3
Kynar wire
Scrap Hookup Wire (18ga. Red, Green, Black)
2N2222 Transistor (Q1) (IR Driver) Q1
2N3055 Transistor (Q2) (IR Driver) Q2
Misc Mounting Hardware
High Power IR Array (Either build it yourself, or buy one from http://www.bgmicro.com/ item# LED1007)
Cigarette Lighter Adapter
Clear Plastic Case
MALE and FEMALE Molex 4 Pin Connector w/Pins



Luckily for us, most of the parts are available at your local Radio Shack, but you may have to visit a specialty electronics store or order from Digi-Key or Mouser to get a few remaining parts. We will be using the IR ILLUMINATOR from BGMicro for the IR Transmitter.  The PC board we will be building this on is up to you on what style you prefer. As you can see in the above picture I am using an “IC Type” but that might not be the one you want to use. A standard PC Board will work perfectly fine. The small plastic case was probably the hardest thing to find (even though you would think it would be the easiest) I ended up finding a perfect case at Office Depot. =) It had 10 million paperclips inside of it. But its up to you where you get it..


Timing Circuit

I suggest you build the timing circuit first, as it is the most complex. What this circuit is doing is creating a variable “pulse” in order to flash our IR Array. I cannot confirm this, but the word on the street is that the best results can be obtained around 10hz or 10 cycles per second. We will use the 500k Potentiometer to control the “blink rate”. What I did for “bench testing” is connect a computer Molex connector to pull 12V from a nearby computer. This is not required, so I didnt include it in the parts list. I then connected the anode of a red LED to Pin 3 of the IC, and the cathode to the 390 Ohm resistor (R5). Connect the other side of the resistor to ground. The LED will now flash with the IR array. At this point we are ensuring that your timing circuit is working correctly, and if it is you will have a fast blinking LED.

Now would be a good time to put your IR Array together. This is probably the most fun part of this project. Nothing like soldering 36 LEDs. All I can say about this is make sure you get the Anode and Cathode correct. (However they are marked very well) Once you have the timing circuit built and tested, the IR Array built, it is time to build a hi-power driver to power the IR Array.

Hi-Power Driver for IR Array

When building the IR Driver circuit, it is IMPERATIVE that you double check polarities on all Capacitors and Transistors. If you happen to use a metal container YOU MUST ISOLATE THE POWER TRANSISTOR (2N3055) FROM THE METAL CASE. Use nylon screws and washers, with electrical tape on the bottom of the transistor to isolate. Failure to follow these instruction will destroy your project!. Once again, check and double check EVERYTHING before you apply power!

Now, cram it all in the Plastic box. Using the soldering Iron, melt a hole in the “Lid” of the box. Mount the IR ARRAY on the outside of the box, using some screws/nuts though the hole you just melted to hold it in place. At this time, this little project should be starting to look pretty good! It is again now a good time to test everything. Having everything hooked and powered up, you should see your RED LED Flashing at a quick pace. That tells us that the timing circuit works, but we need to ensure that the IR Array is blinking along with it. Remember how earlier I mentioned that camera’s CCD can pick up IR light? Well using this knowledge you can use any digital camera or camcorder to see if it is working. Infact, you can even use your camera-phone!


Cut the end off of a 12V Cigarette Lighter Adapter and connect it into your project. As in above, there is already a Molex connector connected to the timing circuit, so lets solder up a male molex to the Cigarette lighter adapter and now you have a quick connect power adapter. (Again, this is not needed, just a simple suggestion) Now you can test it out on the bench easy, or take it to the car. (not that you will be using this in an auto)

At first you may or may not have much luck, because your Hz is probably pretty off. Using the equation

f =10            1.4          
(R1 + 2R2) Ã— C1

R2= 100k, C1=.47uF so R1 must equal ~98k. So using a multimeter set your Potentiometer to 98k and give it a shot. If this doesnt work, try slowly increasing the blink rate.